Sander



July 10, 195] GU|NN 2,560,102

SANDER Filed Oct. 24, 1946 lNVENTOR J [on 0v Gu/N/v.

ATTORNEY Patented July 1 0, 1951 UNITED STATES PATENT OFFICE 2,560,102 SANDER J. Edwin Guinn, Ithaca, N. Y. Application October 24, 1946, Serial o. 705,458

This invention relates to sanders of the type having a power driven abrasive belt which is held against the work to be sanded, and has for its principal object the production of a special form of sander capable of operating on curved surfaces as well as fiat surfaces. Another object is to make possible such a sander in portable form, so that it may be applied to objects too bulky to be moved to a fixed machine. A further object is to protect the abrasive belt from undue wear at its edges when the work is of such a nature as to press it sideways. Another object is to provide it with an adapter which can be inserted for fiat sanding. Various additional objects incident to the foregoing will become apparent as the description proceeds.

Referring now to the drawings forming part of this specification:

Fig. 1 is a view in elevation of the sander, with the abrasive belt operating on a curved surface of the work W shown in broken lines.

Fig. 2 shows the abrasive belt in the straight position with the detachable shoe inserted to permit the sanding of fiat surfaces, the cover plate on the upper portion being removed to show the internal parts, and the lower part being partly broken away and in section.

Fig. 3 is a side view of the sander with the crowned faces of the lower guide pulleys indicated by broken lines, parts of the housing I being broken away and in section.

Similar reference numerals refer to similar parts thruout the various views.

Referring now to Fig. 1 and Fig. 2, the casing fl encloses a motor 2 and reduction gears 3 and 3' which drive a belt pulley on which runs a :belt 5 having a surfacing of abrasive material .such as used in the ordinary sanding machines. For straight sanding this belt has a triangular course extending around pulleys 6 and 5 which :are mounted on a pair of pivoted arms or brackets 11 and I. These arms are capable of yielding inward against the action of the springs 8 whenever the sander is pressed against a rounded piece of work W' so as to permit the sanding belt :5 to wrap partly around the work. The hinges -or pivots of the arms I and l are located at S. Idler pulleys It guide the belt when the arms I and l are moved inward. The pivoted arms .1 and I are slotted and act as belt guides to lead the belt 5 to the pulleys 6 and 8', as well as protect the belt from accidental external contact .at places where it is not intended to work. The outer limit positions of the arms 1 and I can be regulated .by thumb screws H in the studs 2 I l2 which are pivoted into the base of the casing l and carry suitable stop nuts [3. The casing l is provided with handles It and i4 and also a handle [5, which may be provided with the usual control switch l5.

In Fig. 1 a curved or rounded piece of work W is shown to illustrate how the yielding arms I and 1' permit the device to adapt itself to the shape of an object, and while this is a special advantage of the device, the sander may also be used on flat surfaces by inserting an adapter as shown in Fig. 2.

In Fig. 1 it will be seen that the lower ends of the arms I and l are provided with suitable lips 2d and locking clamps 2|. Now, referring to Fig. 2, it will be seen that a metal shoe 23 having corresponding sockets 24 may be inserted on the lips 20 between the arms I and I and locked by the clamps 21 so as to form a continuous straight backing surface for the belt :5 between the arms i and i, This looks the arms I and I in a fixed position and converts the device into the equivalent of a straight sander. The tool may thus do all that an ordinary sander can do and in addition perform many services which a straight sander could not attempt,

In operating the device, particularly on curved or irregular surfaces, the pressure on one edge of the belt may be greater than on the other edge, and if the belt 5 shifts laterally, its edge may tend to cut the guides and casing. In order to strongly center it on the guide pulleys 6 and 6' and prevent undue Wear, the pulleys 6 and 6' are crowned as shown in Fig. 3. In addition it is also preferable to avoid coating the edges of the belt 5 with the abrasive, but to leave a smoother edge such as will not cut the guides in the arms I and I.

All the parts, While enclosed, are readily accessible, and the portion of the case i enclosing the gears 3 and 3' may be made oil tight for quietness and lubrication. The position of this gear box is best seen in Fig. 3. The casing and arms may be of aluminum or any suitable light material, so that the machine can be carried to the work, as is particularly desirable when the work is bulky, such as cars or boats. While the device is thus capable of multiple uses, its cost of construction is but slightly more than the ordinary flat sander.

While I have in the foregoing described a certain specific form by way of example, it will be understood that it is merely for the purpose of illustration to make clear the principles of the invention, which is not limited to the par- 3 ticular form shown, but is susceptible to various modifications and adaptations in different installations as will be apparent to those skilled in the art without departing from the scope of the invention as stated in the following claim.

I claim:

In a sander, the combination of a frame, a drive pulley, a motor, a reduction transmission between the motor and drive pulley, a pivotal swinging arm attached to said frame, an intermediate pulley whose axis is fixed relative to the frame, said axis being in line with the pivotal axis of the swinging arm so that the arm may swing without displacing said intermediate pulley relative to the frame, a swinging pulley on the swinging end of said arm, a further pulley movably mounted on said frame, a sanding belt ex tending around said pulleys, the working portion of the belt for sanding lying between said last mentioned two pulleys, resilient means between 4 the frame and the pivotal swinging arm whereby the belt is maintained in tension at all positions of said swinging arm, said belt being bent around the intermediate pulley at the pivotal end of said swinging arm when the arm is swung inward for sanding pronounced curvatures.

J. EDWIN GUINN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Fowler Apr. 14, 1942 

